Metal corrosion inhibitor for use in aqueous acid solutions

ABSTRACT

The present invention provides an improved metal corrosion inhibitor for use in aqueous acid solutions which is relatively non-toxic and inexpensive. The corrosion inhibitor is a mixture comprised of oligomerized aromatic amines prepared by contacting the still bottoms residue produced in the distillation of quinoline from coal tar with oxygen in the presence of a catalyst.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a Divisional Application of U.S. patent applicationSer. No. 08/855,309, filed May 13, 1997 and entitles "Metal CorrosionInhibitor For Use In Aqueous Acid Solutions" now U.S. Pat. No.5,792,420.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved metal corrosion inhibitorfor use in aqueous acid solutions.

2. Description of the Prior Art

Subterranean hydrocarbon containing formations penetrated by well boresare commonly treated with aqueous acid solutions to stimulate theproduction of hydrocarbons therefrom. One such treatment known as"acidizing" involves the introduction of an aqueous acid solution intothe subterranean formation under pressure so that the acid solutionflows through the pore spaces of the formation. The acid solution reactswith acid soluble materials contained in the formation therebyincreasing the size of the pore spaces and the permeability of theformation. Another production stimulation treatment known as"fracture-acidizing" involves the formation of one or more fractures inthe formation and the introduction of an aqueous acid solution into thefractures to etch the fracture faces whereby flow channels are formedwhen the fractures close. The aqueous acid solution also enlarges thepore spaces in the fracture faces in the formation.

In carrying out acidizing and fracture-acidizing treatments in wells andother similar treatments using aqueous acid solutions, the corrosion ofmetal tubular goods, pumps and other equipment is often a problem. Theexpense associated with repairing or replacing corrosion damaged metaltubular goods and equipment can be very high. In a well treatmentutilizing an aqueous acid solution, the corrosion of metal surfaces intubular goods and equipment results in at least the partialneutralization of the aqueous acid solution before it reacts withacid-soluble materials in the subterranean formation to be treated.Also, the presence of dissolved metals in the aqueous acid solution canbring about the precipitation of insoluble sludge when the aqueous acidsolution contacts crude oil which can in turn severely damage thepermeability of the subterranean formation being treated.

A variety of metal corrosion inhibiting formulations for use in aqueousacid solutions have been developed and used successfully heretofore.Many of such corrosion inhibiting formulations have included quaternaryammonium compounds as essential components, particularly in hightemperature applications. However, problems have been associated withthe use of quaternary ammonium compounds in that they are generallyhighly toxic. Further, the quaternary ammonium compounds which achievehigh degrees of metal corrosion protection at high temperatures arethose which have relatively high molecular weights and high degrees ofaromaticity. Those quaternary ammonium compounds are not readilyavailable commercially and are very expensive to produce. Thus, there isa need for a corrosion inhibitor which is as effective in preventingmetal corrosion as quaternary ammonium compounds but is less toxic andless expensive.

SUMMARY OF THE INVENTION

By the present invention an improved metal corrosion inhibitor for usein aqueous acid solutions is provided which meets the needs describedabove and overcomes the deficiencies of the prior art. The improvedcorrosion inhibitor of this invention is a mixture comprised ofoligomerized aromatic amines which are prepared by contacting the stillbottoms residue produced in the distillation of quinoline from coal tarwith oxygen in the presence of a catalyst at a temperature and for atime sufficient to oligomerize aromatic amines contained therein.

In addition to the mixture comprised of oligomerized aromatic amines andmethods of preparing the mixture, metal corrosion inhibited aqueous acidsolutions are provided by the present invention as well as methods forprotecting a metal surface from corrosion when contacted by an aqueousacid solution using the improved corrosion inhibitor of this invention.

The metal corrosion inhibited aqueous acid solutions are basicallycomprised of water, an acid and an effective amount of a corrosioninhibitor comprised of a mixture of oligomerized aromatic aminesprepared as described above. The acid utilized in the aqueous acidsolutions is preferably selected from the group consisting ofhydrochloric acid, hydrofluoric acid, formic acid, acetic acid, citricacid and mixtures thereof.

The methods of the invention for protecting a metal surface fromcorrosion when contacted by an aqueous acid solution are basicallycomprised of the steps of combining with the aqueous acid solution aneffective amount of a corrosion inhibitor comprised of a mixture ofoligomerized aromatic amines prepared as described above, and thencontacting the metal surface with the aqueous acid solution containingthe corrosion inhibitor.

Thus, it is a general object of the present invention to provide animproved metal corrosion inhibitor for use in aqueous acid solutionscomprised of a mixture of oligomerized aromatic amines, methods ofpreparing the corrosion inhibitor, metal corrosion inhibited aqueousacid solutions containing the corrosion inhibitor and methods ofprotecting metal surfaces from corrosion when contacted by aqueous acidsolutions using the corrosion inhibitor.

Other and further objects, features and advantages of the presentinvention will be readily apparent to those skilled in the art upon areading of the description of preferred embodiments which follows.

DESCRIPTION OF PREFERRED EMBODIMENTS

By the present invention, a mixture comprised of oligomerized aromaticamines having relatively high molecular weights and degrees ofaromaticity is provided which is useful as a metal corrosion inhibitorin aqueous acid solutions. Methods of preparing the mixture ofoligomerized aromatic amines, corrosion inhibited aqueous acid solutionscontaining the mixture and methods of protecting metal surfaces fromcorrosion when contacted by an aqueous acid solution using the mixtureare also provided.

Surprisingly, the mixture of oligomerized aromatic amines of thisinvention functions as a corrosion inhibitor in aqueous acid solutionssubstantially as well as a mixture of equivalent quaternary ammoniumcompounds, i.e., quaternary ammonium compounds having substantially thesame or higher molecular weights and degrees of aromaticity as theoligomerized amines. In addition, the use of the oligomerized aromaticamines is highly beneficial as compared to the use of quaternaryammonium compounds in that the amines are less toxic and are much lesscostly than equivalent quaternary ammonium compounds.

The mixture of oligomerized aromatic amines of this invention isinexpensively prepared from the still bottoms residue produced in thedistillation of pharmaceutical quinoline from coal tar. Such stillbottoms residue contains quantities of quinoline and derivativesthereof, isoquinoline and derivatives thereof, and other aromatic aminessuch as pyridine, picoline, lutidine and the like and their derivatives.The quinoline still bottoms residue starting material is commerciallyavailable, for example, from the Crowley Coal Tar Products Company ofNew York, N.Y. under the tradename "INHIBITOR J™."

A quantity of quinoline still bottoms residue is contacted with oxygenin the presence of a catalyst, e.g., cuprous chloride in an amount inthe range of from about 0.1% to about 2% by weight of the bottomsresidue, at a temperature and for a time sufficient to oligomerize thearomatic amines contained therein. It is believed that the contact withoxygen causes a coupling reaction that oligomerizes the aromatic aminesand thereby increases their overall molecular weights and degrees ofaromaticity. The term "oligomerize" is used herein to mean the couplingof several aromatic amines together and/or to other aromatic compounds.

The contact of the quinoline still bottoms residue with oxygen ispreferably carried out by sparging oxygen through the bottoms residue ata rate of from about 2 to about 30 cubic centimeters per minute per 100milliliters of bottoms residue for a time period in the range of fromabout 8 hours to about 48 hours while maintaining the temperature of thebottoms residue in the range of from about 150° F. to about 225° F.

As mentioned above, the mixture of the oligomerized aromatic aminesprepared as described above functions extremely well as a metalcorrosion inhibitor in aqueous acid solutions, is substantially lesstoxic than quaternary ammonium compounds and is relatively inexpensive.

The improved metal corrosion inhibited aqueous acid solutions of thisinvention are comprised of water, an acid, and an effective amount of ametal corrosion inhibitor comprised of a mixture of oligomerizedaromatic amines prepared from quinoline still bottoms residue asdescribed above.

The water used to form the aqueous acid solutions of this invention canbe any aqueous fluid which does not adversely react with the componentsof the inhibited aqueous acid solution. For example, the water can befresh water, brine, salt solutions and the like.

The acid utilized is preferably an acid selected from the groupconsisting of hydrochloric acid, hydrofluoric acid, formic acid, aceticacid, citric acid and mixtures thereof. The acid is preferably presentin an amount in the range of from about 2% to about 100% by weight ofthe acid solution, more preferably from about 5% to about 38%.

The metal corrosion inhibitor comprised of a mixture of oligomerizedaromatic amines prepared as described above is present in the aqueousacid solution in an amount effective to prevent or reduce the corrosionof metal surfaces contacted by the acid solution. Preferably, thecorrosion inhibitor is present in an amount in the range of from about0.05% to about 3% by volume of the solution.

As will be understood by those skilled in the art, the metal corrosioninhibited aqueous acid solutions of this invention can include a varietyof other additives such as acetylenic alcohols, various corrosioninhibitor intensifiers, sulfide scavengers, solvents, surfactants andother components commonly used in acidizing compositions and known tothose skilled in the art.

The methods of this invention for protecting a metal surface fromcorrosion when contacted by an aqueous acid solution are basicallycomprised of the steps of combining an effective amount of a metalcorrosion inhibitor comprised of a mixture of oligomerized aromaticamines prepared as described above with the aqueous acid solution, andthen contacting 100 milliliters of quinoline still bottoms residuecontaining 1% by weight cuprous chloride with oxygen at a rate of about20 cubic centimeters per minute for 24 hours at a temperature of 175° F.The still bottoms residue used was obtained from the Crowley Coal TarProducts Company under the tradename "INHIBITOR J™." A portion of theresulting mixture of oligomerized aromatic amines was combined withother components to form a first corrosion inhibiting formulation(designated as "Inhibitor A") as follows:

    ______________________________________                                        Inhibitor A                                                                                  Amount, % by                                                   Component      weight of formulation                                          ______________________________________                                        surfactants    18                                                             acetylenic alcohols                                                                           5                                                             solvents (alcohols                                                                           30                                                             and naphtha)                                                                  fatty acids    30                                                             oligomerized aromatic                                                                        17                                                             amines formed                                                                 from oxygen                                                                   treated quinoline                                                             still bottoms residue                                                                        100                                                            ______________________________________                                    

A second corrosion inhibitor was prepared by reacting 200 grams ofquinoline still bottoms residue with 184 grams of benzylchloride inisopropyl alcohol for 8 hours at a temperature of 225° F. to form amixture of aromatic quaternary ammonium compounds. Cuprous chloride wasadded to the mixture to achieve the same weight percent as in InhibitorA. A portion of the mixture was then combined with other components toform a second corrosion inhibitor formulation (designated as "InhibitorB") as follows:

    ______________________________________                                        Inhibitor B                                                                                  Amount, % by                                                   Component      weight of formulation                                          ______________________________________                                        surfactants    18                                                             acetylenic alcohols                                                                           5                                                             solvents (alcohols                                                                           30                                                             and naphtha)                                                                  fatty acids    30                                                             quaternary ammonium                                                                          17                                                             compounds formed                                                              from quinoline                                                                still bottoms                                                                 residue reacted                                                               with benzylchloride                                                                          100                                                            ______________________________________                                    

0.3 milliliter portions of Inhibitor A and Inhibitor B were combinedwith 100 milliliter portions of a 15% by weight aqueous hydrochloricacid solution to form an acid solution containing a concentration of0.3% by weight corrosion inhibitor. In addition, 2 milliliter portionsof Inhibitor A and Inhibitor B were combined with 100 milliliterportions of a 15% by weight aqueous hydrochloric acid solution to formacid solutions containing 2% by weight corrosion inhibitor. Test samplesof the various corrosion inhibited hydrochloric acid solutions wereheated to the temperatures given in Table I below and a preweighed N-80steel corrosion coupon was immersed in each while maintaining thetemperature of the samples for 4 hours. After the four hour testperiods, the corrosion coupons were removed, rinsed and weighed todetermine the rates of corrosion which took place during the tests.

The results of these tests are given in Table I below:

                  TABLE I                                                         ______________________________________                                        Corrosion Tests                                                                                       Corrosion                                                                              Corrosion Rate,                              Temper-        Acid     Inhibitor                                                                              lb/sq. ft.                                   ature, Time,   Sol.     Concentration,                                                                         Inhibitor                                                                            Inhibitor                             ° F.                                                                          Hours   Used     % by weight                                                                            A      B                                     ______________________________________                                        200    6       15% HCl  .sup. 0.3.sup.1                                                                        0.026  0.025                                 250    6       15% HCl  0.3      0.015  0.011                                 300    6       15% HCl  2.0      0.055  0.064                                 ______________________________________                                         .sup.1 Contained 2% by weight of an ethoxylated amine dispersant and 2% b     weight of an antisludging formulation containing dodecylbenzene sulfonic      acid.                                                                    

From the above test results, it can be seen that the corrosion inhibitorof the present invention comprised of oligomerized aromatic aminesprovides metal corrosion protection to aqueous acid solutionssubstantially as well as a mixture of quaternary ammonium compoundsformed from the same still bottoms residue starting material.

Thus, the present invention is well adapted to carry out the objects andattain the ends and advantages mentioned as well as those which areinherent therein. While numerous changes can be made by those skilled inthe art, such changes are encompassed within the spirit of thisinvention as defined by the appended claims.

What is claimed is:
 1. A metal corrosion inhibited aqueous acid solutioncomprised of:water; an acid; and A metal corrosion inhibitor comprisinga mixture of oligomerized aromatic amines prepared by contacting thestill bottoms residue produced in the distillation of quinoline fromcoal tar with oxygen in the presence of a catalyst at a temperature andfor a time sufficient to oligomerize aromatic amines contained therein,said metal corrosion inhibitor being present in an amount in the rangeof from about 0.05% to about 3% by volume of said solution.
 2. The metalcorrosion inhibited aqueous acid solution of claim 1 wherein said acidis selected from the group consisting of hydrochloric acid, hydrofluoricacid, formic acid, acetic acid, citric acid and mixtures thereof, and ispresent in said aqueous acid solution in an amount in the range of fromabout 2% to about 100% by weight of water in said solution.
 3. The metalcorrosion inhibited aqueous acid solution of claim 1 wherein saidcatalyst is cuprous chloride present in said bottoms residue in anamount in the range of from about 0.1% to about 2% by weight of saidbottoms residue.
 4. The metal corrosion inhibited aqueous acid solutionof claim 3 wherein said bottoms residue is contacted with said oxygen ata temperature in the range of from about 150° F. to about 225° F.
 5. Themetal corrosion inhibited aqueous acid solution of claim 4 wherein saidbottoms residue is contacted with said oxygen at a rate in the range offrom about 2 to about 30 cubic centimeters per minute per 100milliliters of bottoms residue for a time period in the range of fromabout 8 hours to about 48 hours.